It's not under-compensation if the worker is getting more of what they want. Even Žižek says that the authoritarian style assumes that you know what the workers want more than they know themselves, and you're assuming that they want monetary compensation more.

He sees this post-modern soft totalitarian style as far more threatening to the worker's liberty. Like with a cult, a prostitution ring, or organized crime, any situation where a person is convinced that they are part of a family in order to exploit them is dangerous to our free society.

Also, in trade guilds, apprentices and journeyman rarely owned their own means of production.

The research also can be used by employees in order to be overcompensated by their bosses! Likewise it can be used to get faster promotions or increase an employee's chances they are chosen to keep their job vs being among those given pink slips should layoffs ever happen at their employer.

In my experience I have seen more employees discover and utilize insights from behavioral economics to their advantage than I have seen instances of managers using it to exploit their employees. Employees who spend a bunch of time researching best strategies to ask for a raise are often way more prepared for such a meeting than their manager.

After a raise, is the new higher salary "fair compensation"? Or is it now "overcompensation"?...Who knows, there is no right answer to this. That is part of Ariely's point. Things like "fairly compensated" or "under compensated" are really subjective - one should be careful not to apply their own such value statements too broadly. everyone needs to chill and rethink their assumptions.

Also don't worry too much. This stuff mainly only matters at the margins (hence these things are "hidden").